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ESSENTIALS OF DIAGNOSIS

  • May be asymptomatic for years (or for life).

  • Severe mitral regurgitation may cause left-sided heart failure and lead to right-sided heart failure.

  • Pansystolic murmur at the apex, radiating into the axilla; associated with S3 when regurgitant volume is great.

  • ECG shows LA abnormality or atrial fibrillation and LVH; radiograph shows LA and LV enlargement.

  • For chronic primary mitral regurgitation, surgery is indicated for symptoms or when the LV ejection fraction (LVEF) is less than 60% or the echocardiographic LV end-systolic dimension is greater than 4.0 cm.

  • In patients with mitral prolapse and severe mitral regurgitation, earlier surgery is indicated if mitral repair can be performed successfully with a high degree of certainty.

  • Patients with functional mitral regurgitation may improve with biventricular pacing. Some may also benefit from surgical intervention or percutaneous repair.

GENERAL CONSIDERATIONS

The components of the mitral valve apparatus include the myocardium below the papillary muscles, the papillary muscles themselves, the chordae, the leaflets, and the mitral annulus. Chordae from both the anterior and posterior leaflets attach to both papillary muscles. When ventricular contraction occurs, the papillary muscles contract first and pull the leaflets toward each other. As the LV pressure rises, the leaflets touch, and the rising pressure in the LV pushes the leaflets together so they support themselves (so-called “keystone” effect). The chordae continue to rein in the mitral valve as systole commences and the annulus contracts. All of these components keep the mitral valve from leaking. Failure of any of these components results in mitral regurgitation. Thus, if the papillary muscles are displaced (as in dilated cardiomyopathy), the chordae are too long or too short, the leaflets are too redundant (as in mitral prolapse), or the annulus does not contract (as in annular calcification or cardiomyopathy), then mitral regurgitation will result. In mitral regurgitation, some clinicians use the Carpentier classification regarding mobility of the mitral leaflets: type 1 is normal, type II reflects increased leaflet motion (as in prolapse or chordal rupture), type III is related to papillary muscle displacement. Type IIa reflects restricted mitral leaflets in both systole and diastole and type IIIb reflects restricted motion in systole only. Mitral regurgitation results in a volume load on the heart (increases preload) and reduces afterload. The result is an enlarged LV with an increased ejection fraction (EF). Over time, the stress of the volume overload reduces myocardial contractile function; when this occurs, there is a drop in EF and a rise in end-systolic volume.

CLINICAL FINDINGS

A. Symptoms and Signs

During LV systole, the mitral leaflets do not close normally for any one or a combination of the reasons stated above, and blood is ejected into the LA as well as through the aortic valve. In acute mitral regurgitation, the LA size is not large, and LA pressure rises abruptly, leading to pulmonary edema if severe. When chronic, the LA enlarges ...

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